This from Dhammamegha:

We have had some trouble at Windhorse Publications earlier this year where access to the site was blocked for potential users. It turned out that there was a Vodafone algorithm that was wrongly applied to us. This applied to both Vodafone contracts and broadband supplied by them, including by third parties. Vodaphone’s algorithm made the judgement that the site contained indecent or inappropriate material. 

Because I’m a Vodafone user, I know that there are other Triratna sites that have had similar trouble. I’m aware of this in relation to Padmaloka and Rivendell sites, which I’ve not been able to access from my phone on occasion.  

Sarvajit helped us to clear the block from the Vodafone side without having to change the end user’s settings. So I wanted to share this in case any other organisations’ websites have the same issue: 

There are two steps: 
1. You can use this website to check whether your site is blocked by Vodafone (or a range of other providers)  https://www.blocked.org.uk/check.  The Vodafone problem, if you have one,  comes up as “SSL Error”.
2. There is an appeals process linked to the site - where you can appeal the categorisation that leads to it being blocked. If you can’t find the link to the appeal - you can contact the BBFC directly here: https://www.bbfc.co.uk/what-classification/mobile-content/appeals
3.  If you have any trouble with the appeal, or it takes a long time for Vodafone to apply the changes one the appeal has been arbitrated (which takes a few days), you can contact them directly on directorsoffice@care.vodafone.co.uk - which is a more direct route than through customer services. 

Anyway - we wanted to share this in case it is of use to other Triratna centres or businesses.